The invention relates to a sensor arrangement for determining the CO2 concentration in an interior space, with an NDIR sensor unit that can determine the number of CO2 molecules on an optical measuring section and therefrom the CO2 concentration in the interior space.
Such sensor arrangements for determining the CO2 concentration in an interior space are frequently used for example in vehicles that travel at different elevations in relation to sea level. For example, there are operating profiles for motor vehicles that are to be operable at elevations between −400 m above sea level to +6000 m above sea level. At an elevation of approximately +5500 m above sea level, the air pressure is already reduced by approximately 50% compared with the standard value for temperature and pressure (STP). Accordingly then non-acceptable measurement deviations occur in the determining of the CO2 concentration.
Measures known from the prior art for determining the pressure for carrying out a pressure compensation involve considerable costs, because pressure sensors, for example compared to temperature sensors, are considerably more cost-intensive. Therefore, in stationary sensor arrangements a pressure compensation is dispensed with, that in view of the comparatively small changes in air pressure that, in relation to STP (1013.25 mbar, 0 degrees C.) amount to ±30 Pa and accordingly in NDIR sensor units can lead to measurement deviations of approximately ±3%, also appears to be acceptable.
However, this does not apply to non-stationary sensor arrangements such as are used for example in motor vehicles.